I Solemnly Swear
by MarauderMagic1
Summary: The untold story of Sirius Black. How he found the friends and love of his life that he didn't expect to meet. And is there another reason as to why Sirius hates Snape so much? I know this summary doesn't completely sell it but please try the story! I unfortunately do not own Harry Potter.
1. Chapter 1

May 1998

The war was over. This was thought that gave Harry Potter much relief as now, for the first time in about seven years, he didn't have to worry about the most evil wizard of all time trying to kill him.

In the aftermath of the battle he had graciously accepted hundreds of congratulations, payed his respects to those who had fought but most of all was now trying to get his life to seem like something that could fit under the world 'normal'. It was in this search for normalcy that he found himself carefully stepping through the door that led into Number 12, Grimmauld Place. Harry hoped that by coming here, not only would he be able to escape the commotion outside, it would also give him time to think. He quietly closed the door behind him trying his best to not disturb the portrait of Sirius's mother, Walburga Black. However it seemed she was asleep - or at least pretending to be.

Without really thinking Harry turned his way towards the stairs and started to make his way up to his godfather's room. He hadn't been back to the house, let alone this room since last summer after he, Ron and Hermione had escaped from Bill and Fleur's wedding. He walked in slowly, gazing around. Unsurprisingly, nothing had changed. He gently sat down on the edge of the bed but quickly shifted in discomfort, realising that he had sat on something. He lifted up the cover and spotted a small leather book which he reached out for. Bringing it up to the light he saw the small, neat, writing on the front. 'Diary' it said. He almost laughed because he had never really pictured Sirius as the type to keep a diary but thinking it through it made sense. He'd probably wanted to record all the pranks that him and James had done. Still, Harry hesitated. It wasn't really his place to read it and he knew that. But him and Sirius had always been truthful and had never really kept secrets and he felt sure that Sirius wouldn't really mind. So with that thought, Harry cautiously opened it to the first page. It was dated 1st September 1971 which, Harry realised, would have been the day that Sirius started attending Hogwarts. He carefully thumbed through the pages looking at the dates of all the entries and noticed that they were fairly inconsistent. Lots more in some years than others. Curiosity getting the better of him, he flipped back to the beginning and began to read...


	2. Chapter 2

**A/N: Sorry this chapter is rubbish, but I hope now some of the more interesting stuff is going to start happening :)**

_1st September 1971_

_Well, I've done it. I've officially proved that I don't belong to my family because I have been sorted into Gryffindor! I think I can say without being dramatic that that has made me happier than I can ever remember being, although I'm sure that when my mother finds out she will break every photo of me that she can find. Oh well, what can you do? Ok wait, I'll go back to this morning. _

_After I said my not so sad goodbyes to Mum and Dad I jumped on the Hogwarts Express to look for a carriage. I was about halfway down the train when, I walked straight into someone. _

"_Sorry," I grinned apologetically._

"_No worries," said the boy who I'd knocked into, "you looking for a carriage too?" The boy had messy brown hair and circular glasses._

"_Yeah, no luck so far though."_

"_Same but there must be one somewhere. I'm James by the way."_

"_Sirius Black. Nice to meet you."_

"_You too, lets find that carriage then."_

_We wandered further down chatting to each other. I liked James, he seemed pretty similar to me. We reached a carriage finally and peeking inside saw only one other boy. _

"_This'll do," said James cheerfully, pushing open the door, "mind if we join you?" he asked the boy inside, who jumped slightly with a mildly shocked look on his face as though he hadn't expected anybody to talk to him. _

"_Sure," he mumbled quietly. Me and James entered the carriage and flopped down onto the seat._

"_I'm Sirius and this is James" I announced to the boy._

"_Peter," he replied sounding slightly more confident, "Peter Pettigrew." _

"_Pleasure to meet you," me and James said at the same time, we turned to grin at each other._

_Just then there was a knock on the glass and the door slid open to reveal another boy about our age , hovering in the door frame._

"_Sorry, everywhere else is full. I'm Remus, do you mind if I sit with you?" _

"_No problem," said James and then pointed to each of us in turn, "Sirius, Peter and I'm James."_

"_Hi," he replied. I noticed that he looked slightly tired but maybe he had just had a bad nights sleep, maybe he was nervous about starting Hogwarts. _

_The four of us talked for quite a while. James was basically my twin (I think our brains work the same way), Remus was easy to talk to although he seemed like he might be the one that would end up telling me and James off in the future. Peter stayed fairly quiet but he still shared his views with us as we talked about everything from the Hogwarts houses to Quidditch teams. I have a feeling that we will be able to stay friends for a long time. (Ugh, sorry that sounded cheesy.)_

Harry laughed at that. Scanning the rest of the page, he briefly read through the rest of the day. When they had first met Lily and managed to annoy her, Sirius and James insulting Snape instantly after meeting him and then they insulted Slytherin house several more times after that. It became clear to Harry how these four had managed to build up such a strong. Their personalities fit together like a jigsaw. He skipped to the Sorting Ceremony. He read about the four of them and Lily being sorted into Gryffindor and Snape, much to Sirius's delight, sorted into Slytherin.

Apparently however, the rest of their first year was uneventful as their were very few other entries under that year, aside from a couple of Quidditch match reviews.

The second year followed a similar pattern apart from the insults and hexes exchanged between Sirius and Snape became worse and more frequent. It wasn't until the third year that Sirius's entries came more often and more intensely. Eager to find out, Harry turned the page...


	3. Chapter 3

_14th September 1973_

_First Quidditch match coming up tomorrow. Gryffindor verses Ravenclaw. James has been training almost every night this week whilst Remus tries to encourage me to complete at least one piece of homework. Tonight, James climbed through the portrait hole with one of his fellow Gryffindor chasers, Alana Tinson. _

"_- and it's a good job I was there when you missed the quaffle that time-"_

"_I didn't miss it!" retorted Alana, "you jumped in front of me so I couldn't reach it."_

"_Well still you didn't catch it did you?" said James and then laughed as irritation became clear on Alana's face, "better luck next time eh?" _

_She scowled at him before storming towards the opposite side of the common room before going to sit with her group of closest friends, one of whom was Lily Evans. This was not a fact that James was unaware of. As he came to sit next to me and Remus he glanced back towards their table automatically running his hand through his hair._

"_Are you trying to get on the wrong side of everyone in that friendship group?" I asked as he flopped down onto the nearest sofa._

_He grinned back at me, "nah she's actually a really good chaser. Don't tell her I said that though," he added._

"_Speaking of things that we probably shouldn't tell people," I added in a lower voice, "me and James think that we might have found a very handy book."_

_James' eyes lit up as he caught onto what I was talking about. "Yes," he joined in, "a handy book that might be able to help us and Peter- where he is by the way?" James said looking around._

"_Help us and Peter," I said quickly picking up from where James had left off so randomly, "to become animagi."_

_With slightly widened eyes Remus asked, "you have? How?"_

_Me and James exchanged a look. _

"_We, uh, had a quick peek in the restricted section of the library last night. Under the invisibility cloak of course," James added hastily._

"_Do you have it?" enquired Remus, "did you get the book?"_

"_Well no," I answered, "we're going to go back and get it. There was, surprisingly, lots of people in the library last night. Couldn't risk them seeing a floating book."_

_Both others nodded in agreement._

"_And you really think that if you if manage it successfully, you'll be able to er, keep me company?"_

"_Almost sure of it," said James proudly._

_We had found out about Remus' "furry little problem" at around Easter in our second year. We had eventually gotten too suspicious and after several interrogation style sessions me, James and Peter managed to get Remus to confess. He said the reason he didn't tell us was because he didn't want us to think he was some kind of out of control monster and he didn't want to lose us as friends. In response James promptly told him he was stupid for ever thinking that and that we would help him in every way we could. Peter and I had agreed with him resolutely. That was when James had his animagus plan. He thought (and the rest of us agreed) that it would be safe, or as close as possible to safe, for us to keep Remus company as animals. And since then we had slowly, carefully begun constructing our plan. And I think that now, we're about to start making real progress._

_3rd October 1973_

_They put up the date for our first Hogsmeade trip today. I'm still slightly surprised that my mum signed the permission slip, but then again I'm still not going to be near her so she's not bothered. _

"_Excited?" James said from appearing from behind me._

"_Uh how would you not be? We get to go Honeydukes, the best sweet shop in the country! I read about it," I added proudly._

"_Ah bless, you've even done your research, that's probably what then, the third time you've ever opened a book?"_

"_That's a bit rich coming from you, surely?"_

_James gave me a small shove, so naturally I gave him a slightly bigger one back. He lost his balance, arms flailing for a second before crashing into the nearest person. Which happened to be, unfortunately for James, Lily Evans._

"_OUCH! Watch it Potter!" she cried, clutching her foot._

_James straightened up instantly, looking slightly embarrassed,"Sorry Evans, but maybe you should watch where you stand in future."_

"You _crashed into _me_!" she fumed._

"_Well, that's only a small detail, we could talk about at Hogsmeade if you want?" James asked hopefully._

_She snorted, "no," she said simply before turning away and calling, "Alana are you ready?" _

_Alana who was just coming down from the girl's dormitory jumped down the last two steps._

"_Yep," she replied, "lets go." The two girls started towards the portrait hole._

_James grabbed my arm and started walking off after them. Lily glanced behind and noticing James behind her rolled her eyes._

"_Leave us alone Potter."_

"_Uh, I'm not sure whether you've forgotten but we're in the same class. We're not following you, we're just being good students and going to class on time."_

_A laugh escaped my mouth and James gave me a mischievous grin as he and I both know that the words "good students" were rarely used to describe us._

_Sighing, Lily linked her arm through Alana's and set off at a much faster pace not looking back this time. Despite this being another obvious rejection, James was smiling._

"_One day," he said confidently, "one day she'll come round."_

"_Of course she will," I replied with only a hint of sarcasm. James had asked Lily out for the first time at the end of second year which she had answered with a blunt 'no'. However James being James, was undeterred and since then has repeatedly asked her out, strangely getting more confident with each rejection._

"_She's just denying her feelings," he had insisted after the third rejected offer._

"_Yeah that or she does actually hate you," I had responded (not very encouragingly). _

_As we headed away from the common room and towards the grounds for Herbology ,James was still smiling quite smugly._

"_You'll see," he sang cheerily, "just you wait and see."_


	4. Chapter 4

_5th October1973_

_Me and James went to get the book on becoming an animagus from the library today. We had planned to get it yesterday, but after we all fell asleep by the fire in the common room, we thought it would be better if we got it when we were more alert._

_Before we left Peter wished us luck. "We don't need luck," snorted James, "we have skill."_

_I laughed and Remus gave a small smile but Peter didn't seem entirely satisfied. With a quick farewell wave, me and James slipped under the invisibility cloak and clambered out of the portrait hole. Quietly we made our way to the library, our only light was that which was given out by the flickering candles on the wall. When we got to the library I scanned the room quickly. As far as I could see it was empty._

_"All clear," I whispered._

_"No angry librarian," James whispered back sounding half disappointed. (James loved to annoy the strict librarian and actually so did I. I reckon we were the only people in the school that could get away with it as well, as she seemed to have a bit of a soft spot for us and couldn't really stay mad at us for too long.)_

_Swiftly we made our way through the main area and into the restricted section._

_"There it is," James said and pointed to a fairly large and old leather bound book. I reached out my hand and carefully pulled out the book. On the front in big silver letters it said, 'The Essential Guide to the Art of Animagi' and then underneath that in slightly smaller writing it said ' A detailed yet understandable explanation of the process, the theory and the practical by Bertie Montoe.'_

_A considerable amount of dust had settled on the top of the pages and when I opened it, I saw that the pages were yellowing although the writing remained quite clear._

_"That's the same one isn't it?"_

_"Yeah."_

_"Right, let's go then."_

_When we got back to the common room, Peter and Remus were still sitting by the fire although the majority of other people had seemed to all ready have gone to bed. In fact the only other two people there were Lily Evans and Alana Tinson. They seemed to be doing homework as they were both holding quills and leaning over long pieces of parchment, although they seemed to be more interested in their conversation than the textbooks in front of them. I flopped down onto the chair next to Remus and James onto the one opposite me, next to Peter._

_"Did you get it?" he asked, sounding a lot more excited now that he could see that we'd managed to complete our mission without getting caught. I grinned indicating the book that James was now holding with a smug expression on his face._

_"Piece of cake really wasn't it Sirius?"_

_"Definitely, not challenging at all."_

_"Let's see it then!" demanded Remus._

_"With pleasure," said James as he flipped open the front cover. We all gathered around it eagerly._

_"Ugh," I groaned," so much writing!"_

_"It's all important though, you really can't afford to miss anything out," said Remus._

_"I didn't say I wouldn't read it, I just said there was a lot of it!"_

_Just at that moment there were several quiet thuds and we all looked up to see Lily and Alana had closed their books and were packing up their stuff._

_"Hey Evans," said James automatically. I rolled my eyes. Half the time I think he doesn't even think about it, it's just such a habit that he automatically talks to her; never to much success._

_She glanced up and she too rolled her eyes. Grinning slightly Peter and Remus turned back to the book but James stayed looking at Lily._

_"Need any help?" he asked, indicating the actually rather large pile of parchment and books the two of them were putting away._

_"I can manage thanks," Lily replied acidly and out of the corner of my eye I'm sure I saw Alana smile but she quickly looked down as if to hide it and slid another book into her bag._

_James just carried on grinning somewhat stupidly._

_The two girls seemed to have packed away all their stuff now and started to walk towards the stairs that led towards the girls' dormitory. But as we were watching a quill fell out the bottom of Alana's bag. I looked at her to see if she'd stop but she was still walking. Apparently she hadn't realised. Without really thinking I jumped out of my chair and ran over to pick up the quill._

_"Ala- uh Tinson wait!" I called. She turned around surprised. "You dropped this," I said waving the quill._

_"Oh - how?" she asked more to herself than me. She looked at her bag trying to find the source of the problem and saw in the bottom corner of bag there was a medium sized hole. She took out her wand, pointed it at the gap and muttered "Reparo!" and stitches immediately jumped across the gap, sealing it._

_"Thanks," she said looking back up at me._

_"No problem," I replied looking back at her. "She has lovely eyes," I thought, a very clear blue. I was just thinking this when I realised she was holding out her hand, 'does she want me to take it?' I thought confused, but then I realised I was still holding her quill. Hastily I handed it back to her._

_"Thanks," she repeated._

_"Yeah no problem," I said again. We stood there for just a moment longer before she said, "Well goodnight then."_

_"Night," I replied. She smiled and turned around to join Lily who had been waiting this whole time at the bottom of the staircase. They walked up the stairs and then disappeared into the girls' dorm._

_I too, turned around and with a strangely satisfied feeling made my way back to the other three._

_"What was that about?" James asked curiously as I sat back down._

_"I was just doing my good deed for the day," I replied._

_"Hmm if that's all..."_

_"And what does that mean?"_

_"Nothing, nothing..." James trailed off but a smile was playing on his lips._

_8th October 1973_

_I realised that I forgot to mention the result of the first Quidditch match against Ravenclaw. We won! James and Alana scored most of the goals between them ( although Ravenclaw did get some in) and our Seeker, Eveline Fir, caught the snitch just over half an hour in._

_We're only about a quarter of the way through 'The Essential Guide to the Art of Animagi'. Remus is insisting that we read it from cover to cover before attempting any of the magic._

_"It's just safer," he said firmly._

_I will admit though, the book is interesting and that's a pretty decent compliment coming from me. The trouble is finding the time to read it. We usually manage to get in a chapter when the four of us are in the common room, after we've done some homework, but we can only really get it out when it's nearly empty as well. It would look quite suspicious otherwise and I don't think anyone would believe that we were reading just for the sake of it._

_James, for some reason, keeps smirking or nudging me whenever Alana is near by. After this had happened for about the billionth time, I decided I'd had enough._

_"What are you doing?" I demanded rather loudly causing several people nearby to look round, slightly alarmed._

_"How do you mean?" he replied innocently._

_"All these funny looks you keep giving me whenever Alana's around!" I said, "and all the nudges! I think I may have developed a bruise because of you."_

_"Oh wow, sorry mate, I didn't realise you had such sensitive skin!"_

_Peter snorted from next to James. Lupin was looking down at a book but he still had an amused expression on his face._

_"You're changing the subject."_

_James sighed. "Well isn't it obvious?"_

_"Well, no."_

_He sighed again except this time more dramatically. Whatever this was, he was certainly making the most of it. "You fancy Tinson," he declared._

_"What?" I spluttered, "what, what do you...?What?"_

_"You know, Alana Tinson," James said in a voice that suggested he thought this was the most obvious thing in the world, "blonde, pretty, chaser for Gryffindor, friends with -"_

_"I know who she is!" I interrupted._

_"Ah good! Well you see, I think you fancy her."_

_I just stared at him. I, Sirius Black, was used to being the person that other people fancied but I myself, had never had a crush on anyone._

_"I don't know what you're talking about," I responded, "besides, I thought it was you that went chasing after girls not the rest of us."_

_"Hey, I never said that you were chasing after her or anything! And I only chase after one girl not girls," he corrected._

_"Whatever," I replied going back to my abandoned homework._

_"I'm right," he carried on in the same confident voice he used when talking about his chances with Lily, "trust me, I'm right."_


	5. Chapter 5

_15th October 1973_

_Considering that now we're quite far into the school term me and James decided it was about time to pull a prank. Not a big one of course just a small one to get us going. James put in this huge order for dungbombs which arrived this morning, in time for us to do the prank this afternoon. It's really a simple one but if it goes right it will be incredibly satisfying. Severus Snape, we've found out through careful observation, can be counted on to be on the fourth floor corridor __at 4:00 pm__every week day where he will walk right to the end, to the corner, sit down and stick his nose in a book._

_All me and James planned to do was set off our entire collection of dungbombs. James had found a spell that would make them go off when they detected human presence so Snape wouldn't even need to touch them. We thought it was a pretty genius plan._

_"Are you going to come Remus?" James asked at about half past three that afternoon._

_"No, I don't think so," he lowered his voice, "full moon's coming up. I'm getting a bit tired."_

_We nodded in understanding. "What about you Pete?"_

_"Yeah I'll come," he said enthusiastically. He looked thrilled to have been invited._

_"Right that's sorted then. Got the invisibility cloak James? Just in case?"_

_He picked up his bag and a pulled out a small section of silvery material._

_"Check. Lets go then, we can get there early." And the three of us crawled through the portrait hole._

•••••••••

_"All set. Now we wait in here until we see old Snivellus," said James closing the door on the store cupboard we were hiding in. For a store cupboard, it was actually pretty roomy with a small window in the door and it was almost opposite the corner where Snape would sit so we could look out and watch his reaction._

_"We've got about ten minutes," I said checking my watch. James grinned and so did Peter although he seemed to be unable to decide whether he should be more excited or nervous. _

_"Wait do you hear that?" James said suddenly. Peter and I both pressed our ears against the door. Sure enough we there was a sound coming from outside. Footsteps._

_"Do you think Snape's early?" Peter whispered but James shook his head._

_"The footsteps are too light, it's not him." He pulled the invisibility cloak over his head and looked out the window._

_"Alana Tinson," he muttered._

_"What do we do?" Peter asked, panicked._

_Me and James looked at each other. We both knew we couldn't let her get past this door or the dungbombs would explode when she went by and not Snape. Her footsteps were getting louder, she was getting closer._

_Without really thinking, I opened the door and slipped out behind her._

_"Sorry," I whispered in her ear and before she could realise what was going on I slipped one hand over her mouth and wrapped my other arm around her waist, hoping that she wouldn't hit me, and pulled her into the store cupboard to join James and Peter. I could feel my heart thumping for some reason louder than usual in my chest._

_As James shut the door behind us, she stamped on my foot with surprising force causing me to instantly let go of her as my hands now clutched my toes._

_"What the hell?" she demanded angrily, glaring around at all of us._

_"Please keep your voice down," said James who was still standing by the door and glancing out the window every now and then._

_She shot him a furious look before saying, "somebody better explain." _

_But in all fairness, she was now speaking more quietly._

_"Look, " I started, in what I hoped was a calming voice, "really we were just helping you, I -"_

_"Helping me?" she spluttered indignantly," I was just minding my own business when you come and drag me in here-"_

_James cut her off, "You should look at it as a compliment. Sirius doesn't drag just any girl into a store cupboard."_

_Pink tinged her cheeks slightly but she remained looking angry. "I'm going to leave," she announced and made towards the door but before she could reach it James threw himself in front of it, blocking her way._

_"No! Just wait for five minutes," he requested, "then you can leave."_

_Alana's eyes narrowed suspiciously. "What's going on?"_

_"We're just pulling a little prank," I explained," and we didn't want you to be caught up in it and if you'd carried on walking then you would have been."_

_Judging by the look on her face she couldn't tell whether or not I was telling her the truth, but at least now she wasn't trying to get past James, she just stood there with her arms crossed and her eyebrows raised._

_"Thank you," said James gratefully. Peter was staring at her in awe, probably because she had stood up to us which was something not many people usually did._

_And then again we heard footsteps. James quickly looked out the window again and this time he grinned._

_"Here he comes!"_

_Peter and I rushed back to the door while Alana watched us curiously._

_Sure enough, Snape was walking quickly down the corridor to his corner; closer to the dungbombs. Now he was just within touching distance... BOOM! They exploded right in his face, clouds of foul smelling gas going everywhere. The three of us all collapsed with silent laughter and even Alana was biting her lip trying to stop her smirk._

_Snape was furious. He angrily waved away the smoke as he looked around for someone to blame. Spotting our store cupboard he started to make his way over._

_"Quick," said James, still laughing, as he threw the invisibility cloak over the four of us and we shuffled in to the corner._

_The door burst open and Snape basically fell in the door. You could clearly see the fury etched on his face. He scanned the room, his eyes passing over the corner where we stood, but of course he couldn't see us. He left again, shutting the door with a slam. We stayed still for a moment longer until we heard Snape's footsteps retreating back down the corridor._

_"That was brilliant!" Peter exclaimed._

"_Did you ever doubt it?" I said smugly._

"_Now you can go," James said to Alana, swinging the door open as he did so._

_Alana seemed to be debating whether to laugh or tell us off but took the invitation. _

"_Thank you," she replied before breezing out of the open door._

_I stared after her until she disappeared round the corner and out of sight. When I turned back around, James was grinning with a satisfied look on his face._

"_What?" I challenged but his only answer was a laugh before saying, "we should inform Remus of our success._

_As soon as we entered the common room Remus looked up eagerly._

"_So? Did everything work?" _

"_Like a dream," I said as I settled into the nearest arm chair._

"_Sirius got an added bonus as well," James added, and to answer Remus' quizzical look, "Alana Tinson," he said simply._

"_Ah," Remus said with a nod of understanding. _

_I opened my mouth to speak but Remus cut me off._

"_Don't even try to deny it."_

"_Deny what?"_

"_Seriously?"_

"_Mate, you clearly fancy Tinson," James interjected, "I've told you once and I will tell you again."_

_For the rest of the evening I brushed off their claims but once I got into bed all I could hear was their voices in my head. And the more I thought about it, the more I gradually began to realise that I did in fact, have feelings for Alana Tinson._

** A/N: Thank you for reading! Please review and/or follow and I hope you're enjoying the story! I will try to update soon :)**


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